The present invention relates to freeze-dried food products showing smooth melting in mouth and a process for preparing the same.
As foods freeze-dried and eaten as it were, there are ice creams, freeze-dried fruits and the like, and a process for preparing the same has been disclosed, for instance, in Japanese Patents. 47-19011 (B) and 1-218554(A). These freeze-dried food products have low moisture content and porous structure, since the products have been prepared by freezing moisture or water contained in raw materials thereof and removing the moisture by sublimation, so that parts wherein frozen water presented become vacant spaces. Therefore, the conventional freeze-dried food products give a fragile feeling, which like of snack confectioneries.
However, the freeze-dried food products obtained by simple freeze-drying the raw materials for the food in accordance with the conventional process may give some rough feeling, when it melts in mouth, provides foreign feeling by absorbing saliva in mouth or adheres on mucous membrane in oral cavity, and thus it cannot be said as the food showing smooth melting in mouth.
Objects of the invention, therefore, are to provide freeze-dried food products showing smooth melting in mouth and a process for preparing the food products.
The process according to the invention comprises steps of dissolving in water raw materials for the food or making the same into a form of paste through a micronizing treatment; emulsifying the food materials in the form of solution or paste by adding thereto heated oil or fat for the food and an emulsifier to mix the same for preparing an emulsion; while stirring the emulsion, cooling the same to prepare semi-frozen cream-like product; distributing the semi-frozen product into a mold; further cooling the product to cause solidification due to freezing; and freeze-drying the frozen solid product.
The freeze-dried food products according to the invention is characterized by those obtained by the above process and show smooth melting in mouth.
In more concrete explanation of the process according to the invention, water-soluble food materials are made into an aqueous solution, or food materials insoluble to water or difficult to dissolve in water are micronizingly processed to make it in the form of paste; the solution or paste is mixed with the oil or fat heated at temperature of 35-70xc2x0 C. and an emulsifier, by if necessary adding water to adjust water content of the mixture to 30-70% by weight; the emulsion is cooled until temperature becomes xe2x88x921-xe2x88x926xc2x0 C., while stirring the same, to obtain semi-frozen cream-like product; the creamy product is distributed into molds or vessels to stand for overnight at temperature of xe2x88x9240-xe2x88x9220xc2x0 C. to cause complete solidification due to freezing; and then the frozen product is freeze-dried to prepare final food products having moisture content of about 4% or more less.
When the food materials are made into the solution or paste, an emulsifier may be added and if necessary, heated to 35-70xc2x0 C.
When the food materials in the form of solution or paste is prepared or such food materials are mixed with the liquified fat and emulsifier, starch hydrolysate, lactose, sugar, dextrose, sorbitol, maltitol, polydextrose or the like may be added.
There is no specific limitation on the food materials and thus the invention can be applied for an ice cream, cow""s milk, yogurt, cheese and the like milk products, chocolate, cookie and the like confectioneries, nuts, fruits, vegetables and others. The term of xe2x80x9cchocolatexe2x80x9d includes general one to be prepared by mixing cacao mass, cocoa, cocoa butter, sweetening material, powdered milk and the like, rolling and conting treatment as well as analogous products thereof.
When the food material is chocolate and its thermostability is required as the freeze-dried final food product, it is preferable to add a gelatinizing agent such as crystalline cellulose into the emulsion in an amount not exceeding 6% by weight, for instance 2-3% by weight to total solid amount.
As the oil or fat for the food to be used in the process according to the invention, palm oil, palm kernel oil, coconut oil, soybean oil, cotton-seed oil, peanut oil, cocoa butter, substitute oil and fat of cocoa butter and milk fat can be exemplarily listed. Among them, it is suitable to use the cocoa butter, substitute oil and fat of cocoa butter, milk fat or any combination thereof.
Such oil or fat for the food is composed in an amount of 10-80 (W/W) % and more preferably 30-60 (W/W) % to the weight of solid amount of the freeze-dried food product.
The freeze-dried food product obtained by the process according to the invention has porous structure with fine texture, in comparison with products obtained by conventional freeze drying processes and thus is excellent in smooth melting in mouth.